Suspension System
Suspension Components, Types and Issues
The suspension of your vehicle is another system of the vehicle that vehicle owners easily take for granted, maybe because it is mainly out of sight and out of mind. It is easy to underestimate the importance of this system and we hope to rectify this.
Harris (2017) mentions an important aspect to consider when discussing the importance of the suspension, namely that of vehicle dynamics (the study of the forces at work on a moving vehicle). Automobile engineers consider these dynamics from two perspectives: the ride (a vehicle’s ability to smooth out a bumpy road) and handling (a vehicle’s ability to safely accelerate, brake and corner). These two perspectives, the ride and the handling, encompass three important principles – road isolation, road holding and cornering. Each of these three principles present its own set of problems, and this is where the suspension comes into play. It is the suspension, with its various components, that provides solutions to all the problems that these three principles present. The suspension system is mainly responsible for reducing the uncomfortable effects whenever you drive over any uneven surface. Imperfections on any road surface make for a bumpy ride, so you need a system that will absorb the energy of the wheels, allowing the frame and body to ride undisturbed, while the wheels follow bumps in the road. This is where the system of springs and shock absorbers (as part of the suspension system) comes into play; it reduces the impact of bumps and it gives the driver and occupants in a vehicle a more comfortable ride. Apart from giving more comfort, the suspension also improves vehicle safety and performance. After all, what is the use of having all the desired power and acceleration, but lacking the ability to control the vehicle?
The suspension is not as simple as some may think. Tom Esposito (2016) highlights this complexity when he says that there are many parts involved that makes this system not only very complex but also see to it that the system function properly. The suspension system consist of several components, including the chassis, which holds the cab of the vehicle. He mentions six components that are basic to any suspension system, namely the springs (that supports the weight of the vehicle and absorb excess energy from road shocks), the dampers (shock absorbers) and the struts. The anti-sway bar (that shifts the movement of the wheels and stabilizes the vehicle), the ball joints, and the spindle.
If you are not enlightened about the suspension as a system and the components mentioned here that make up this system, then this article have one aim – to enlighten you about the extent and importance of this system, about the different types of suspensions, as well as to draw your attention to suspension related issues you may encounter.
Suspension Components
Springs
The following types of springs may be found in a suspension system.
Coil Springs
These are the most common types of springs in use; they compress and expand to absorb motion. A coil spring is actually a heavy-duty torsion bar coiled around an axis, wound in a spiral shape. Springs rarely need maintenance or replacement.
Leaf Springs
These springs are mainly in use in heavy-duty vehicles and trucks. You may picture this type of spring as the ones used on horse-drawn carriages. It consist of several layers of leaf metal bound together as one leaf.
Dampers
The presence of dampening structures in a vehicle’s suspension system is important because if there are only springs present, the vehicle will still give a bumpy ride. This is because a spring will extend and release the energy it absorbs from a bump at an uncontrolled rate until all of the input energy is depleted. The following dampening components make sure that this is reduced to a greater degree.
Shock Absorbers
The shock absorbers will not be discussed here because it is discussed separately as part of its own article. Click here to read more about the shock absorbers.
Suspension Struts
This is basically a shock absorber mounted inside a coil spring. Struts perform mainly two jobs; dampening shocks like shock absorbers and it also provides structural support for the vehicle’s suspension. Follow the link mentioned above if you want to read more about the strut.
Torsion Bar
In the case of a torsion bar, the twisting properties of a steel bar provides coil-spring like results. One end of the steel bar is anchored to the frame of the vehicle while the other end of the bar is attached to a wishbone. Whenever the vehicle encounters a bump, the vertical motion transfers to the wishbone and then to the torsion bar, which twists along its axis to provide the required spring force.
Anti-sway / Anti-Roll Bars
These metal rods span the entire length of the axle and effectively joins each side of the suspension together. Working together with the shocks or struts, they give additional stability in the form of a level ride and sway reduction. Tom Esposito (2016) explains why these bars are of importance. When cornering, or turning, forces want to roll your vehicle’s body to the outside of the turn. Anti-sway/roll bars work to counteract this force and keep the wheels in contact with the ground.
Ball Joints
The ball joint is a pivot between the wheels and the suspension of your vehicle. In the front suspension, on most vehicles, there are upper and lower ball joints on both sides.
Spindle / Upright
In an automobile, the spindle is a part of the suspension system that carries the hub for the wheel and attaches to the upper and lower control arms.
These are then the main parts of the suspension system, and we will see why they merit mentioning when we come to the part about taking care of your suspension and identifying possible problem areas with the suspension. Before we do that, let us have a look at the different types of suspensions used in motor vehicles.
Types Of Suspension
There is indeed not only one type of suspension for all vehicles; there are different types of suspension and they greatly rely on axle arrangement. Suspension can be either dependent or independent front or rear. Let me explain.
Dependent Front
This type of suspension have a rigid front axle that connects the front wheels with each other (the left and right wheels share a single, solid axle). It is not a very preferable type because it makes your vehicle prone to swaying; it is also difficult to adjust wheel alignment, and it increases weight due to the lack of springs.
Independent Front
Wheels move independent of each other.
MacPherson Strut
This is the most widely used type of front suspension because it is a single cohesive unit. It combines a shock absorber and a coil spring as one unit.
Double Wishbone (A-Arm)
Two wishbone arms connect to the wheel, the system incorporates coil springs and shock absorbers to absorb vibrations. Each wishbone, which has two mounting positions to the frame and one at the wheel. The coil spring and damper are on a strut linked to the bottom wishbone and chassis. This type of suspension minimizes sway and works well in larger vehicles.
Trailing Arm
This is very similar to a double wishbone, with the difference that it have specially shaped suspension arms connected to the chassis that moves parallel to it. This is an older system and best recognizable by that of a VW Beetle suspension.
Twin I-Beam
Exclusively used in Ford’s F-series trucks; it is a mixture of a solid beam axle (split in two) with a trailing arm suspension, thereby excluding the dependent front suspension issues.
Transverse Leaf Spring
With the leaf spring positioned across the entire width of the vehicle, it connects to the lower A-arms of the double wishbone on both sides. The centre of the leaf spring is mounted to the vehicle’s subframe.
Dependent Rear
Rear suspensions have greater latitude because they do not consider the steering mechanism.
Solid Axle
With this type of suspension, you can either have a leaf- or coil springs mounted on both ends of the drive axle.
4-Bar
Applicable to both front- and rear-wheel drive vehicles, it can be considered the favourite system in street- and classic hot rods.
Independent Rear
The same independent front system can be used in the rear. If both the front and back suspensions are independent, then all of the wheels are mounted and sprung individually, resulting in four-wheel independent suspension.
De Dion
This is a combination of a trailing arm fully independent suspension and a solid beam axle suspension. This system gives better traction; the extra weight due to a lack of springs is also reduced. The downside to this system is that it requires two CV joints for every axle; brake replacement is also a difficult task due to the placement of the brakes.
Suspension Issues
We looked at the main suspension components, and as in the case of any component that wears down, so a worn suspension component may reduce the stability of the vehicle and reduce driver control. An already worn component will also accelerate wear on other suspension components. Always keep that in mind. Components such as shocks and struts (not to downplay other components) have so much to do with the handling of a vehicle, that they can be considered critical safety features. A worn shock and strut can allow excessive vehicle-weight transfer from side to side and front to back, which reduces the tyre’s ability to grip the road and to perform well during handling and braking.
Suspension issues can be difficult to diagnose. Faulty suspension components can wreak havoc on your vehicle and make it unsafe to drive, so please do pay attention to how your vehicle handles. Listen for any strange noises and address any problems immediately. Let us look at the most common suspension issues, as highlighted by Harris (2017).
Rough vehicle ride
When shocks or struts are wearing out, you may begin to feel every bump in the road. A rough ride is an obvious sign that your vehicle’s suspension needs attention. If you have a suspicion of worn shocks or struts, you can always try the bounce test… With your vehicle in park, place all of your body weight on the front end, release and observe how the vehicle responds. If it bounces back and forth three or more times, it might be due to worn shocks and/or struts that need replacing. Shocks keep your tyres on the road; when they cannot do this anymore, your vehicle will bounce all over the place.
A worn out leaf spring can also contribute to a bouncy ride. The presence of a busted leaf spring can be verified by checking if the vehicle lean back while in a parked position. Vehicles with leaf springs are designed to be nose down to accommodate extra weight in the rear. If your vehicle appears to sit level, it could be extra proof of an issue with a leaf spring.
Drifting or pulling during turns
With a failing suspension system, you will feel the vehicle “drift” or “pull” when you are turning. This may happen when the shocks are no longer keeping the vehicle’s body stable against the centrifugal force of a turn, increasing your risk of a rollover. If you feel this sensation while turning, have it checked.
Nose-dives or squats when braking
When your vehicle’s body lurch forward and downward nose-first when you apply the brakes firmly, it might be a sign of worn shocks. This is dangerous because it will affect your ability to stop your vehicle in time, if needed. Give attention to your vehicle’s shocks or struts whenever you notice the following additional signs: your vehicle “rolls” to the side when cornering (it leans side-to-side); your vehicle “squats” during acceleration (it leans backward).
Uneven tyre treads
If you notice that your tyre’s tread is wearing down unevenly, or if you notice balding spots, this is often a symptom that the suspension is not holding the vehicle evenly. Have this looked at.
Oily shocks
Have a look at the shocks or struts of your vehicle. If they look greasy or oily, there is a good chance they are leaking fluid and are not working properly. Address this issue by having it verified and replaced.
Pulling to one side while driving
A vehicle pulling to either side is a common sign of suspension problems but it can also be something else that is wrong. Any of the following may be reasons for such a pull: uneven tyre pressure, uneven tyre wear, poor alignment, bad tie rods or steering rack, or even a sticking brake calliper.
One corner of the vehicle is sitting low
When your vehicle is standing still on a level piece of ground, but one corner sits lower than the other does, you likely have a damaged spring. A clunking noise when going over a bump may confirm this. Cornering will also be compromised because a damaged spring cannot support the weight. Test the springs by pushing down on the trunk. On release listen to how the suspension reacts. If you hear a creaking or squealing sound, you definitely have a problem with the shocks, springs, bushings or related parts, so have it addressed.
Bump steer
A poorly aligned suspension can cause your vehicle’s wheels to be oriented at such an angle that any little bump will make it turn to either side.
These are the eight most common symptoms and causes of suspension problems. You may prevent these by following a few very simple measures:
- Check your owner’s manual (if available) for an estimate of your damper and suspension system lifespan.
- Make sure you know when to replace your shocks and struts – this will depend greatly on your driving style and road conditions under which you drive.
- Check your shocks or struts frequently for any leakages.
- Pay attention to how your vehicle handles. If you notice the ride becoming more and more bouncy and uncomfortable, take your vehicle to have the suspension system checked.
- Have your vehicle’s ball joints checked at least twice a year as they can wear and can cause your vehicle to wander. Ball joints can separate and cause you to lose control.
The suspension system is one of the most important aspects to your comfort and safety when you are driving. If you suspect that there is a problem with your vehicle’s suspension system, schedule an appointment and bring it to your nearest Steves Auto Clinic right away. Your safety and the safety of others depends on a suspension system that is in a good working condition.
Sources consulted during the writing of this article:
- Bonnici, D. 2016. Car Suspension: What it is and how it works. Online available at: https://www.whichcar.com.au/car-advice/car-suspension-what-it-is-and-how-it-works
Accessed on 4 August 2018. - Collins, D. 2018. Complete guide to Car Suspensions. Online available at: https://www.carbibles.com Accessed on 4 August 2018.
- Esposito, T. 2016. 7 Warning signs that your car has a suspension system problem. Online available at: http://www.autotechwestislip.com/7-warning-signs-that-your-car-has-a-suspension-system-problem/ Accessed on 4 August 2018.
- Harris, W. 2017. How car suspensions work. Online available at: https://auto.howstuffworks.com/car-suspension.htm Accessed on 4 August 2018.
Images used in this article:
- RDC Automotive. Online availbale at: https://www.tdcautomotive.com/eibach-pro-kit-lowering-springs-front-only-30-mm-e7011-120.html Accessed on 22 Aug 2018
- BDS leaf springs. Online available at: https://www.realtruck.com/bds-leaf-springs/ Accessed on 22 Aug 2018